Most aircraft comprise an electrical on-board network which is supplied with electrical energy by generators which are mechanically connected to engines of the aircraft. In order to save weight and to simplify the construction of an engine, for example a turbine, it is possible to dispense with a gear unit which has a transmission ratio and couples the generator with the engine and to directly connect the generator to the engine. This can lead to the on-board network frequency changing depending on the rotational speed of the engine. In this case, the on-board network of the aircraft is generally configured in such a way that it can be operated at a variable frequency. For example, a generator coupled directly with a turbine can produce a frequency of between 360 and 800 Hz, which is fed into the on-board network.
Many electrical loads in the aircraft, which for example include pumps or fans, are operated by electrical energy from the on-board network. Owing to the variable frequency, it may be necessary to decouple said loads by means of frequency converters.
In particular if motor-driven loads are to be operated at a desired rotational speed on an on-board network having a variable frequency, decoupling by means of direct current links and inverters may be necessary. This approach can, owing to the high network quality requirements, be very expensive and also relatively difficult, since complex filters and rectifier circuits (due to the high network quality requirements) may be used.
Examples of electrical loads of this type include fans for ventilation, as described in DE 10 2008 025 960 A1 and US 2011/0111683 A1. In addition, other objects, desirable features and characteristics will become apparent from the subsequent summary and detailed description, and the appended claims, taken in conjunction with the accompanying drawings and this background.